Closed head or closed orifice fire sprinkler systems are economically constructed, typically requiring no automatically opening deluge valve, and requiring no auxiliary heat sensitive deluge valve actuating means. Closed head fire sprinkler systems typically contain pressurized water, and closed orifice sprinkler heads at the terminal water output ends of such system withhold the water in the absence of fire. Upon exposure of one of the sprinkler heads of a closed head sprinkler system to heat from a fire, a heat fusible link incorporated in the sprinkler head fractures, opening such sprinkler head for local water dispersion.
A chief disadvantage of closed head sprinkler systems is that each sprinkler head of such system is individually responsive to heat. The opening of one of the sprinkler heads of a closed head sprinkler system does not open any other sprinkler head within the system. If a closed head sprinkler system were installed within a high risk fire hazard zone, such system would be unable to effectively suppress a rapidly spreading fire. Thus, closed head sprinkler systems are not commonly utilized in high risk fire hazard zones.
Fire sprinkler systems utilized in high risk fire hazard zones are necessarily adapted to instantly inundate an entire fire hazard zone with water in response to a localized fire ignition point within the zone. Through inundation of an entire zone, water flow is established in advance of a rapidly spreading fire, increasing the likelihood that the sprinkler system will effectively suppress the fire. Such fire sprinkler systems, commonly referred to a deluge systems, utilize open orifice sprinkler heads at the terminal water output ports of the system. The open terminal ends of a deluge system cannot withhold water under pressure. Therefore, an automatically opening deluge valve for restricting water flow at the input end of the system is normally utilized. The deluge valve of a deluge fire sprinkler system is normally closed, necessitating the provision of means for automatically opening such valve upon the occurrence of a fire at any point within the fire hazard zone. Known means for automatically opening such deluge valves comprise a fluid pressure actuated main valve installed in combination with a network of pressurized tubes, such network being co-extensive with the water pipes of the deluge system. The terminal ends of such network of tubes typically have heat sensing fluid release valves. Upon actuation of any one of the fluid release valves of the network of tubes, such network experiences an overall drop or rise in fluid pressure, actuating the deluge valve to allow a flow of pressurized water throughout the water pipes of the system, causing substantially simultaneous emission of water from the system's open sprinkler heads.
Another known means for automatically opening the deluge valve of a deluge sprinkler system comprises an electrically actuated main valve installed in combination with a network of electric lines installed co-extensively with the network of water pipes. The terminal ends of the network of electric lines commonly include electric switches sensitive to heat, ultraviolet or infra-red radiation, the closing or opening of any one of which opens the deluge valve, releasing a flow of pressurized water throughout the system.
Open head deluge fire extinguishing systems typically are more expensive to install and maintain than closed head systems because of the requirement of installing and maintaining a fire sensing network of tubes or electrical lines in addition to the fire extinguishing water distribution piping. The instant inventive deluge fire sprinkler system eliminates such additional expense by allowing fluid contained within the water pipes of the system to serve as an integral part of its means for automatically opening its deluge valve. By eliminating the need of a separate heat sensing network, the expense of the instant inventive deluge fire sprinkler system may be equal or less than that of a closed head system.